This invention relates to imaging processing, and more particularly to methods for producing full parallax autostereoscopic displays, such as full parallax holograms.
In recent years, there has been rapid improvement in graphics display techniques aimed at providing a perception of three dimensions. Three dimensional images displayed on a two-dimensional screen using conventional display technology contain limited three dimensional cues such as obscuration, depth effect, and illumination effects. For enhanced three dimensional displays, special architectures depart from conventional two dimensional displays.
Two enhancements for three dimensional displays are stereopsis and parallax. Stereopsis may be achieved with various hardware such as shutters and headgear. It may also be achieved without special equipment, and the resulting displays are then referred to as xe2x80x9cautostereoscopic displaysxe2x80x9d. When parallax is provided in the vertical as well as the horizontal dimensional, the display is referred to as a xe2x80x9cfull parallaxxe2x80x9d autostereoscopic display. Full parallax autostereoscopic displays include autostereoscopic displays such as full-parallax holographic stereograms, full-parallax lenticular or xe2x80x9cfly""s eyexe2x80x9d displays, and full-parallax raster-barrier or parallax-barrier displays.
Methods for producing full parallax spatial displays require unconventional computer graphic rendering methods, such as the double frustum rendering method. This method uses two opposing camera frusta, one at either side of the image plane. An implementation of the double frustum method was developed by Michael Halle and Adam Kropp, and is described in the technical paper, xe2x80x9cFast Computer Graphics Rendering for Full Parallax Spatial Displays,xe2x80x9d Proc. Soc. Photo-Opt. Instrum. Eng. (SPIE), 3011:105-112 (Feb. 10-11, 1997).
One aspect of the invention is a computer-implemented method of rendering data for producing a full parallax autostereoscopic display of a digital scene. First, an image plane is defined, the image plane passing through at least a portion of the scene. The image plane is divided into a plurality of contiguous image elements. Two camera frustra are simulated, one on each side of the image plane. Each camera frustrum has an associated eyepoint. A near clipping plane of the frustra is located on the image plane. For each image element, a distance between the eyepoint and the near clipping plane that would avoid near clipping of the scene is determined. Based on this determination, one or more near clipping plane distances are selected, and the camera frustra are positioned along the z axis of the image plane in accordance with the selected near clipping plane distance(s). For each of the image elements, image data is generated from each camera. This image data is combined to render the scene.
The method is especially useful for constructing holograms. Distortion caused by the near clipping plane is greatly reduced, and hence overall image quality is improved.